Science is full of facts and numbers and formulæ and things to remember. Keeping it all straight can be a chore, even for the geniuses. As a result, over time people have developed interesting ways of remembering the order of things in groups and categories.

Cross-stitch reminder of resistor codes, courtesy of Adafruit.

Another way of remembering the color values:

First two (or three) digits: Bad boys rape our good girls, but Violet gives willingly – get some now ->

Black, Brown, Red, Orange, Gold, Green, Blue, Violet, Grey, White (gold, silver and none refer to the tolerance band)

Resistors can be ever more complicated than in the early days when this mnemonic was developed. Six-band resistors have three significant digits, a multiplier, a tolerance band, and a temperature coefficient.

339Ω with a 1% tolerance.

39 kΩ with a 10% tolerance

Mnemonics are a good way of remembering other things as well. Most of us became good friends with Roy G. Biv in school:

Partial rainbow over Utah Lake, Mt. Timpanogos in the background. The order of colors in a rainbow are Red, Orange, Yellow, Green, Blue, Indigo, Violet.

There are numerous mnemonics for remembering the order of the planets in the solar system; my favorite is found in Robert A Heinlein’s Have Space Suit, Will Travel: Mother Very Thoughtfully Made A Jelly Sandwich Under No Protest (he used “T” for Terra, and included the “A” for Asteroids.)

And for what it’s worth, to Hell with the AIU. Pluto may be smaller than some of the other TNU’s and dwarf planets out there, but it was part of the solar system since Tombaugh discovered it, and by the dessicated skull of Mogg’s grandfather, there it stays. Randall Munroe of XKCD fame disagrees, and I give him mad props for being a genius, but as far as I’m concerned,

Huge selection of mnemonics here.

The Old Wolf has spoken.